what are the differences between simple network management protocol
(SNMP) and secure socket layer (SSL) in terms of functionality?  what
are the main functions do they serve respectively?

Hello Jyw,

As already noted, these two protocols provide almost completely
different capabilities.

SNMP is described in RFC #1157 with applications described in RFC
#2573. Usually you also should understand Management Information Base
(MIB) in RFC #1156.
  http://www.faqs.org/rfcs/rfc1157.html
  http://www.faqs.org/rfcs/rfc2573.html
  http://www.faqs.org/rfcs/rfc1156.html
The Simple Network Management Protocol - SNMP describes techniques for
managing networks. It describes:
 - network management stations
 - network elements (or systems)
and the messages and information exchanged between them. The goals for
this standard were to keep costs relatively low while providing a way
to effectively manage the network equipment.

A list that shows the scope of SNMP related documents is at
  http://www.hio.hen.nl/rfc/snmp/
which lists SNMP version 1 and 2 related standards.

Note that the SNMP standard does not necessarily indicate how network
equipment is to be managed in a secure manner. Some companies do this
with separate networks for management and general data transfer.

SSL as most often implemented is described in RFC #2246.
  http://www.ietf.org/rfc/rfc2246.txt
You will notice that the title of this "Request For Comment" is
Transport Level Security. TLS basically takes the place of SSL and on
page 4, it notes that TLS version 1 is almost identical to SSL version
3.0 as published by Netscape. There is a longer compatibility section
on page 65. The goals of the protocol are to:
 1. Establish a secure connection.
 2. Different implementations will work with each other.
 3. Create a framework that is extensible (e.g., new methods).
 4. Be relatively efficient.
For reference, SSL 3.0 is described at Netscape's site at
  http://wp.netscape.com/eng/ssl3/

More tutorial information is at
  http://www.ssl.com/sslprotocol.asp
the "how it works" does not try to use too much technical material.

Please also note that Netscape has a patent on the basic methods but
has made it available royalty free. See the notes in the RFC for more
information on this.

 --Maniac

They are completely different in application and use.

SSL is an encryption scheme that encrypts browser traffic from your
computer to the server.

SNMP is a protocol for Network managment.  Here are some more complete
definitions

The Secure Sockets Layer (SSL) is a commonly-used protocol for
managing the security of a message transmission on the Internet. SSL
has recently been succeeded by Transport Layer Security (TLS), which
is based on SSL. SSL uses a program layer located between the
Internet's Hypertext Transfer Protocol (HTTP) and Transport Control
Protocol (TCP) layers. SSL is included as part of both the Microsoft
and Netscape browsers and most Web server products. Developed by
Netscape, SSL also gained the support of Microsoft and other Internet
client/server developers as well and became the de facto standard
until evolving into Transport Layer Security. The "sockets" part of
the term refers to the sockets method of passing data back and forth
between a client and a server program in a network or between program
layers in the same computer. SSL uses the public-and-private key
encryption system from RSA, which also includes the use of a digital
certificate.
TLS and SSL are an integral part of most Web browsers (clients) and
Web servers. If a Web site is on a server that supports SSL, SSL can
be enabled and specific Web pages can be identified as requiring SSL
access. Any Web server can be enabled by using Netscape's SSLRef
program library which can be downloaded for noncommercial use or
licensed for commercial use.

TLS and SSL are not interoperable. However, a message sent with TLS
can be handled by a client that handles SSL but not TLS.

Simple Network Management Protocol (SNMP) is the protocol governing
network management and the monitoring of network devices and their
functions. It is not necessarily limited to TCP/IP networks.
SNMP is described formally in the Internet Engineering Task Force
(IETF) Request for Comment (RFC) 1157 and in a number of other related
RFCs.

Extra geeky SNMP info link below:

http://www.faqs.org/rfcs/rfc1157.html